I. Field
The following description relates generally to wireless communications and more particularly to fall back procedures in a wireless communication environment.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content, such as voice, data, video, and so forth, and to communicate information regardless of where a user is located (e.g., inside or outside a structure) and whether a user is stationary or moving (e.g., in a vehicle, walking). These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available systems resources (e.g., bandwidth and transmit power). Multiple-access systems include Frequency Division Multiple Access (FDMA) systems, Time Division Multiple Access (TDMA) systems, Code Division Multiple Access (CDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple mobile devices. Each mobile device can communicate with one or more base stations through transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices. The reverse link (or uplink) refers to the communication link from mobile devices to base stations. These communication links can be established through single-input-single-output (SISO) systems, multiple-input-single-output (MISO) systems, multiple-input-multiple-output (MIMO) systems, and so forth. In addition, mobile devices can communicate with other mobile devices (and/or base stations with other base stations) in peer-to-peer wireless network configurations.
Communication systems, such as circuit switched (CS) systems and packet switched (PS) systems, have been developed. CS systems were developed as part of the Global System of Mobile Communication (GSM). PS systems can operate on the basis of Internet Protocol (IP), such as a Universal Mobile Telecommunications Standard (UMTS) or an Internet Protocol Multimedia Subsystem (IMS). There has been a change from CS systems to PS systems and other systems due to the need to convey different types of payload data or media, such as voice, audio, images, executable program code, text data, and other forms of payload data.
In some geographic areas, CS systems and PS systems can exist in parallel and mobile device users within the geographic area desire adequate coverage, regardless of the system supported by the user's mobile device. However, an IMS system is unable to determine if the terminating CS network is available if the Single Radio Voice Call Continuity (SRVCC) network supports Idle mode Signaling Reduction (ISR). Therefore, terminating calls may be sent to the PS domain even though the terminating calls should be sent to the CS domain, which can lead to dropped calls and other problems that can result in negative user experiences.